Allergic purpura

Definition

Allergic purpura (AP), a form of vasculitis (inflammation of the blood
vessels), is a disease characterized by inflammation of the small arterial
vessels (capillaries) in the skin, kidneys, and intestinal tract. Symptoms
include a purple spotted skin rash, abdominal
pain
, gastrointestinal upsets, and joint inflammation, swelling, and pain.
Although the exact cause of the disease is unknown, it often develops
following a recent viral or bacterial infection of the respiratory tract
and is an abnormal reaction of the immune system to the infection.

Description

AP may occur suddenly, or it may develop slowly over a period of weeks.
The characteristic rash is always present in the disease. The rash begins
as areas of redness and as small
hives
, which may develop anywhere on the body, but especially on the legs and
buttocks, and may itch. The rash is caused by inflamed capillaries
rupturing, allowing small amounts of blood to accumulate in the
surrounding tissues. Through time the rash changes color from red to a
bruised, purple color. Each rash spot will last about five days, and the
rash can reoccur several times. The skin rash is the most obvious symptom
of AP but is not the most serious, for the joints, gastrointestinal tract,
and kidneys may also be affected.

Joint inflammation (arthritis), especially of the knees and ankles, occurs
in two-thirds of the children affected by AP. The joints become swollen,
tender, and painful with movement; the pain may be debilitating. However,
the arthritis usually clears up with no permanent damage.

Gastrointestinal symptoms are a result of inflammation and bleeding of the
capillaries in the gastrointestinal tract, including the mouth, esophagus,
stomach, and intestines. Most children with AP experience severe abdominal
pain,
vomiting
(possibly with blood), and bloody stools.

The most serious complication of AP is kidney inflammation (nephritis),
which occurs in almost half of older affected children. Symptoms include
blood and protein in the urine. Most children whose kidneys are affected
recover fully, but about 10 percent later develop more serious chronic
kidney disease. In 80 percent of those with kidney involvement, the kidney
disease develops within the first four weeks of illness.

Children younger than three years who contract AP have a shorter, milder
course of the disease with fewer recurrences. Older children are more
likely to have more serious symptoms.

AP is also called Henoch-Schonlein purpura, named after the two German
physicians who first recognized and described it in the 1880s. AP is also
referred to as anaphylactoid purpura or vascular purpura.

Demographics

AP is the most common acute vasculitis affecting children. In the United
States, the prevalence of AP is approximately 14 to 15 cases per 100,000
population.
Approximately 75 percent of cases occur in children between the ages of
two and 11, with peak prevalence in children aged five years. AP is rare
in infants and younger children. Boys are affected more often than girls
(the female-to-male ratio is 1.5-2:1). Most cases occur in late fall and
winter. Adults can also develop the disease.

Causes and symptoms

Causes

AP is caused by reactions of antibodies binding with foreign proteins,
called antigens. In some cases, the antigen-antibody complexes become too
large to remain suspended in the bloodstream. When this occurs, they
precipitate out and become lodged in the capillaries, which can cause the
capillary to burst, resulting in a local hemorrhage.

The source of the antigens that cause AP is unknown. Antigens may be
introduced by bacterial or viral infection, because more than 75 percent
of children with AP report having had an infection of the throat, upper
respiratory tract, or gastrointestinal system several weeks before the
onset of AP. AP may also be caused by allergens, which are otherwise
harmless substances that stimulate an immune reaction. Drug allergens that
may cause AP include penicillin, ampicillin, erythromycin, and quinine.
Vaccines possibly linked to AP include those for typhoid,
measles
, cholera, and yellow fever. Food allergens, cold exposure, and insect
bites
have also been associated with AP.

Symptoms

The onset of AP may be preceded by a
headache
, fever, and loss of appetite. Most children first develop an itchy skin
rash. The rash is red, either flat or raised, and may be small and
freckle-like. The rash may also be larger, resembling a bruise.
Rashes
become purple and then rust-colored over the course of a day, and fade
after several weeks. Rashes are most common on the buttocks, abdomen, and
lower extremities. Rashes higher on the body may also occur, especially in
younger children.

Joint pain and swelling is common, especially in the knees and ankles.
Abdominal pain occurs in almost all children with AP, along with blood in
the stools. About half of all affected children show blood in the urine,
low urine volume, or other signs of kidney involvement. Kidney failure may
occur due to widespread obstruction of the capillaries in the filtering
structures called glomeruli. Kidney failure develops in about 2–5
percent of all affected children and in 15 percent of those with elevated
blood or protein in the urine.

Less common symptoms include prolonged headache, fever, and pain and
swelling of the scrotum, scalp, eyelids, lips, ears, backs of the hands
and feet, and perineum. Involvement of other organ systems may lead to
heart attack (myocardial infarction), inflammation of the pancreas
(pancreatitis), intestinal obstruction, bowel perforation, or acute
intussusception (a twisting inversion of the lining of the bowel).

Diagnosis

Diagnosis of AP is based on the symptoms and their development, a careful
medical history, and blood and urine tests.
X rays
or computed tomography (CT) scans may be performed to assess
complications in the bowel or other internal organs. In some cases a renal
biopsy may be useful to determine the extent of kidney involvement.

When to call the doctor

A doctor should be consulted if a child exhibits symptoms of AP. After a
child has had an episode of AP, the doctor should be called if the child
experiences sudden increases in abdominal pain, which may indicate a bowel
infarction or perforation, or if the child exhibits decreased urine
output, indicating kidney disease.

Treatment

Most cases of AP resolve completely without treatment. Nonetheless, a
hospital stay with supportive treatment is usually required because of the
possibility of serious complications. Non-aspirin pain relievers may be
given for joint pain. Corticosteroids (such as prednisone) are sometimes
used to alleviate gastrointestinal tract inflammation but have not been
shown to be effective for associated kidney problems. Kidney involvement
requires monitoring and correction of blood fluids and electrolytes. Salt
intake should be restricted. A child with AP should be monitored until
abnormal urinary findings subside.

Children with severe kidney complications may require a kidney biopsy so
that tissue can be analyzed. Even after all other symptoms subside,
elevated levels of blood or protein in the urine may persist for months
and require regular long-term monitoring.
Hypertension
or kidney failure may develop months or even years after the acute phase
of the disease. Kidney failure requires dialysis or transplantation.

Surgery may be necessary to correct acute intussusception of the bowel.

Prognosis

AP may be mild, lasting only two or three days. However, for those
children with moderate to severe symptoms, AP may last for four to six
weeks, with relapses in about half of all children within six weeks,
especially if the child contracts another respiratory infection or is
exposed to the allergic agent. Relapses can occur up to seven years after
the initial disease. Full recovery occurs in most cases without kidney
involvement. However, one fourth of children who have kidney symptoms
still have detectable problems years later. There is a higher likelihood
of permanent renal damage with a higher number of recurrences.

Prevention

If the initiating trigger for a case of AP is identified in an affected
child, everything possible should be done to ensure that the child is not
exposed to that substance again. If the cause is thought to be a bacterial
infection, such as
strep throat
, prophylactic antibiotic treatment is sometimes given once the infection
has been treated to prevent recurrence.

Parental concerns

Parents should be vigilant regarding recurrence of symptoms after their
child has had AP. Parents should also realize that although severe kidney
involvement is rare, if it does occur, it may require aggressive treatment
and long-term care. If the child does have long-term kidney problems, the
stress of the illness can often be mitigated by parents joining a support
group in which members share common experiences and problems.

KEY TERMS

Capillaries
—The tiniest blood vessels with the smallest diameter. These
vessels receive blood from the arterioles and deliver blood to the
venules. In the lungs, capillaries are located next to the alveoli so
that they can pick up oxygen from inhaled air.

Glomerulus
—Plural, glomeruli; a network of capillaries located in the
nephron of the kidney where wastes are filtered from the blood.

User Contributions:

CAN YOU DEVELOP LUMPS IN THROAT, GROIN AND UNDERARMS YEARS AFTER CONTRACTING HSP. WOULD IT SHOW UP IN BLOOD TEST. LONG TERM EFFECTS OF THIS DONT APPEAR ANYWHERE. ITS LIKE MY SONS IMMUNE SYSTEM HAS BEEN AFFECTED.

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